From DE 198 48 733 A1, an emergency release device is known for a parking-lock mechanism for a vehicle with an automatic transmission, in which the electronic parking-lock mechanism, which is integrated into the automatic transmission, is actuated when the vehicle is in normal operating mode by way of the person operating the vehicle actuating a gear selector device by engaging the position “P”. The parking-lock mechanism is functionally connected to the device by way of a transmission mechanism that is affixed to a static part of the motor vehicle outside the passenger compartment of the motor vehicle by way of which the parking-lock release mechanism can be manually engaged or released, as the case may be. The device also comprises a towing hook for towing the vehicle, which is in a position that releases the parking lock mechanism during towing so that the parking-lock mechanism is securely released during towing.
The device or, as the case may be, the towing hook has two final positions and the towing hook can be immobilized in the final position in which the parking-lock mechanism is unlocked. This ensures that the parking lock mechanism, when it is in an unlocked state, remains securely deactivated even when alternating forces act on the mechanism. If the parking lock mechanism is to be reactivated and the output of the vehicle determined, the immobilization of the device can be released by way of a force being exerted once on the device and the parking-lock mechanism is then reactivated by way of a spring mechanism.
In addition, there is an actuating device known from practice for operating a locking mechanism, particularly for operating a parking-lock latch of a motor vehicle that has a drive chain configured with an automatic transmission, the actuating mechanism having at least one piston unit, displaceable in an axial direction and arranged in a housing, which is admittable with a fluid and which, depending on the fluid pressure, can be operated in the opening direction of the locking mechanism against a spring mechanism working in the direction of the closing mechanism. In addition, the device is configured with a detent element for holding the piston unit in an axial position equivalent to the open state of the locking mechanism, the detent element being automatically activated when the piston unit is in an axial position that is equivalent to the open state of the locking mechanism.
In addition, the actuating device is configured with an electromagnetic operating mechanism for operating a release element intended for deactivating the detent element. The piston unit is functionally connected with an emergency release mechanism by way of which the piston unit can be brought into the axial position that is equivalent to the open state of the locking mechanism.
In the case of the actuating device known from practice or, as the case may be, the known parking-lock actuator, the parking lock is released by way of hydraulic or pneumatic force and engaged by way of spring force. In order for the parking lock to remain in an open state even when there is no fluid pressure, the release element is held by way of the electromagnetic operating mechanism against a spring brake in a position that does not deactivate the detent element so that the piston unit is held by the active detent element in the axial position that is equivalent to the open state of the locking mechanism and the locking mechanism or the parking-lock latch does not engage with a parking-lock wheel that is connected to the power train.
If the function of neither the electromagnetic operating device nor the hydraulic or, as the case may be, pneumatic system is available, the parking lock of the motor vehicle will be engaged by way of the spring device that acts in the closing direction of the locking mechanism through activation of the locking mechanism. This results from the fact that when the electromagnetic operating mechanism is not electrified, the release element is displaced by the spring brake assigned to the release element in such a way that the detent element is deactivated. This means that when there is a system failure in the motor vehicle during which neither hydraulic nor pneumatic pressure can be produced and when electrical power from the vehicle electrical system is not available either, the parking lock is assigned to engaged status as the preferred position, which arrests the output of the vehicle.
This performance is desirable in cases where the transmission can be operated when electrical power fails by way of a hydraulic or pneumatic emergency program and the parking lock can be prevented from engaging. In a vehicle configured in this way, the driver still has the possibility of maneuvering the vehicle to a location determined by the driver and parking the vehicle there in a secure state.
However, if the vehicle is not configured with a hydraulic or pneumatic emergency program, the parking lock that interacts with an actuating mechanism of the prior art will automatically engage so that output is disadvantageously arrested and the driver can initially move the vehicle only with the assistance of external auxiliary devices, such as a tow truck, for example.
Of course, it lies within the discretion of a person skilled in the art to configure the actuating device with an emergency release mechanism in the manner known from the state of the art, by way of which the parking lock can be manually deactivated. However, releasing the parking lock requires action on the part of the driver in the form of operating the emergency release mechanism, which, however, is not desirable in some situations.
The task set for the present invention was, therefore, to provide an actuating device for operating a locking mechanism, in particular a mechanism for operating a parking lock of a drive chain of a vehicle configured with an automatic transmission, with which the parking-lock latch would remain in the last position selected in the event of a system failure and, in which case, it would be possible to simply deactivate or activate manually, as required by the driver.